Haakon became earl after his father was killed by King Harald Greycloak's men in 961. He warred with King Harald for some time, until he was forced to flee to Denmark and Harald Bluetooth. In Denmark he conspired with Harald Bluetooth against Harald Greyhide.

Haakon Jarl arranged the death of Harald Greyhide around 971 with the connivance of Harald Bluetooth, who had invited his foster-son to Denmark to be invested with new Danish fiefs. Civil war broke out between Haakon Jarl and the surviving brothers of Harald Greyhide, but Haakon proved victorious.[3] After this, Haakon Jarl ruled Norway as a vassal of Harald Bluetooth, but he was in reality an independent ruler. For Harald, he attacked Götaland and killed its ruler Jarl Ottar. When Haakon was in Denmark, Harald Bluetooth forced him to accept baptism and assigned him clergymen to take to Norway to spread Christianity. When a favourable wind came for Haakon to leave, he commanded the clergymen to return ashore.[4]

Around 973-974, he went to Denmark to help Harald Bluetooth of Denmark in his defense against the Holy Roman Emperor Otto II. Otto's forces successfully opposed an attempt by Harald to throw off the German yoke. After that Haakon paid no taxes to Denmark.

Haakon Jarl is a central figure in Håkon og Kark which is performed annually at the Korsvikaspillet festival in Korsvika in Trondheim. The play is based on the story of Haakon Jarl and Tormod Kark as portrayed in the Sagas by Snorri Sturluson. The first play was a poetic tableau that was made in connection with the 800-year anniversary of the Lade Church (Lade kirke) in 1989 and repeated two years later. In 1995, Idar Lind wrote a new script. The music is composed by Frode Fjellheim.

Haakon Jarl's life also received literary treatment by Danish poet Adam Oehlenschläger, in his tragedy Hakon Jarl, written in six weeks in 1805 during a stay in Halle, after reading Snorri's Heimskringla. The theme is the conflict between paganism and Christianity. There is an English translation by J. C. Lindberg.[6] Oehlenschläger's play later formed the basis for Smetana's symphonic poem Hakon Jarl.[7]